The present invention relates generally to bearings, and more particularly to a switchable, hydraulically damping bearing.
A switchable, hydraulically damping bearing is known from German Patent 42 38 752 C1. The pulling and compressing movements of the bearing empties an air chamber via a non-return valve to increase the bearing""s spring stiffness. The use of the non-return valve makes it possible to discharge air from the air chamber without any outside assistance. Air intake into the air chamber is accomplished by opening an intake valve, connecting the air chamber to the atmosphere. The diaphragm then returns to its original position.
The object of the present invention is to further develop a switchable, hydraulically damping bearing of the type described above so that it has a high spring stiffness and good damping properties as needed, while maintaining very small dimensions and a low mounting height.
This object is achieved according to the present invention by a supporting bearing and a bearing member. A bearing spring made of an elastomeric material elastically connects the supporting bearing and the bearing member. A working chamber and a compensating chamber are formed by the supporting bearing and the bearing member. The chambers are arranged consecutively in the direction of the vibrations. Both chambers are filled with damping fluid, and a partition separates the chambers on the sides facing each other. A damping conduit is provided in the partition to allow fluid communication between the chambers. At least a portion of the working chamber is delimited by an elastic diaphragm that also delimits an air chamber on the side facing away from the working chamber. The air chamber is connected to the environment by a switchable intake valve or a non-return valve, depending on the operating state of a supported engine. The air chamber can be filled with air flowing through the non-return valve when the intake valve is closed and the bearing executes pulling movements, thereby increasing bearing rigidity.
According to one embodiment, the supporting bearing can have a core and a core plate that is adhesively connected to the bearing spring. The core plate is sealingly connected in a positive-locking manner to the core. The advantage of this arrangement is that the multi-part supporting bearing can be easily adapted to a variety of bearing types. For example, it is possible to connect cores of different designs to the same core plate, requiring only the joining areas of the cores to have the same design. In addition to cores having different designs, the cores can also be made of different materials adapted to the application at hand.
The air chamber is preferably formed by the diaphragm, core, and core plate. The diaphragm preferably extends at right angles to the direction of the initiated vibrations and is sealingly connected to a flange of the core plate extending in the axial direction. A diaphragm that extends at right angles to the direction of the initiated vibrations has the advantage (compared to diaphragms that extend in the direction of the initiated vibrations) that it can tolerate a direct load without reversing the flow and thus without any losses. Integrating the arrangement into the core requires practically no additional mounting height, making it possible to give the bearing a compact design. A geometric delimitation from the nozzle diaphragm system is also advantageous for adjusting the function.
The bearing spring and the diaphragm are preferably made of the same material and are designed as one continuous piece. Both the bearing spring and the diaphragm are preferably vulcanized along with the core plate in a single step to ensure economical and simple production. If especially soft diaphragms are required, however, a separate diaphragm is more practical. Separate diaphragms are also more practical with larger diameters.
The intake valve can be operated by electromagnetic means. Different operating methods, such as pneumatic or hydraulic operation, are possible. Electromagnetic operation of the intake valve is especially well suited to applications in engine bearings, due to their switching precision.
The intake valve is preferably connected to the engine management system of an internal combustion engine and connects the air chamber to the environment while the internal combustion engine is idling or is closed at nonidling speeds.
The operation of the bearing according to the present invention will now be described. The bearing is preferably used as an engine bearing to support an internal combustion engine. While the internal combustion engine is idling, the intake valve is open so that the pressure in the air chamber equals the atmospheric pressure. In this mode of operation, the bearing""s spring stiffness is comparatively low to insulate or eliminate idling vibrations.
At speeds above idling speed, i.e., during vehicle operation, the valve is closed. The air chamber is thus hermetically sealed against the environment. During vehicle operation, the damping fluid is transferred back and forth between the working and compensating chambers through a damping conduit. This damps high-amplitude, low-frequency vibrations. In this operating mode, the diaphragm limiting the air chamber undergoes very little deformation, since the air chamber is closed and the air it contains alternately compresses and expands during vibration damping. At high vibration amplitudes the bearing is subjected to large pulling movements. This results in a rebounding movement which produces a partial vacuum in the working chamber. This partial vacuum expands the diaphragm in the direction of the working chamber, increasing the volume in the air chamber. Because the intake valve is closed, the only way to equalize the partial vacuum in the air chamber is for the air to flow from the environment into the air chamber through the non-return valve. When the bearing reverses its load from a pulling movement to a compression movement, the non-return valve closes automatically. The air mass previously entering the air chamber during the pulling movement is thus trapped in the air chamber. The higher pressure in the air chamber therefore produces a higher bearing rigidity. The higher bearing rigidity improves the damping action of the bearing.
The valve and the non-return valve preferably form a single preassembled unit. This simplifies mounting the unit onto the bearing and minimizes the danger of mounting errors.
The core can be designed with a largely circular shape, with the unit being connected to the core. For example, it is possible to arrange the unit in a central recess in the core and screw it onto the core. The connection between the air chamber and the atmosphere, either via the intake valve or via the non-return valve, is formed by a hollow cylindrical core screw or a hollow cylindrical stay bolt. Components of this type allow the unit, composed of the valve and non-return valve, to be attached to the supporting bearing, and also form a connecting line for the air between the environment and the air chamber.
The core and/or the unit can have at least one stop pad. The stop pad limits extreme movements at the diaphragm during bearing compression movements. At high-amplitude, low-frequency vibrations, for example, pressure peaks occur within the working chamber. The stop pad also avoids exposing the diaphragm, which is much thinner than the bearing spring, to unwanted high mechanical loads during bearing compression movements. This gives the bearing uniformly good service characteristics during a long service life.
The diaphragm can have surface texturing on the side facing the stop pad. The surface texturing can be formed, for example, by a random texture in the form of stop nubs to prevent noise when the diaphragm comes into contact with the stop pad.
The diaphragm can be subjected to elastic pretension so that it rests against a stop pad under elastic pretension when the bearing is subjected to a static preload. This gives the bearing better damping characteristics.
At least the bearing spring can be surrounded by a heat protection cover on its outer circumference. The heat protection cover is preferably held on the supporting bearing so that it remains stationary and prevents a connected internal combustion engine from radiating heat directly onto the bearing spring. It is also advantageous to protect the damping fluid located in the working and compensating chambers from unwanted exposure to high temperatures. This helps maintain good service characteristics.